Coaxial water and air jet–assisted laser micromachining of titanium

A ring-type nozzle combining a jet of air and water was employed in this study for improving the quality of laser-cut channel and limiting thermal damage along the cut. A nanosecond pulse laser equipped with the water–air jet nozzle was used for producing a microgroove on the surface of commercially pure titanium. The influences of average laser power, air pressure, and water flow rate on groove dimensions and size of damage region were experimentally investigated. The results revealed that using high air jet pressure together with high water flow rate provided a narrow and deep groove with little recast deposition. The selections of air jet pressure and water flow rate were also found to be nonlinearly dependent to each other for creating a microgroove with high aspect ratio. With the aid of weighted sum method, an optimum condition of the coaxial water and air jet–assisted laser micromachining of titanium was 30-W average laser power, 2-bar air jet pressure, and 2.5-l/min water flow rate. Under this condition, a high aspect ratio groove with negligible recast and no heat-affected zone was achievable by using the proposed technique.